Analysis and Approaches for IBDP Maths Ebook 1 | Page 266

Your Practice Set – Analysis and Approaches for IBDP Mathematics
86
Paper 1 Section B – Game problems
Example
In a game, two standard six-sided dice are tossed. Let X be the sum of the scores on the
two dice.
(a)
Find
(b)
(i) P( X � 10) ;
(ii) P( X � 10) ;
(iii) P( X �11 X � 9) .
Jenna plays a game where she tosses two dice.
If the sum is 10, she wins 2 points.
If the sum is greater than 10, she wins 1 point.
If the sum is less than 10, she loses k points.
Find the value of k for which Jenna’s expected number of points is zero.
[6]
[7]
Solution
(a) (i) There are 3 ways such that X � 10 (A1) for correct value
P( X � 10)
3
�
36
1
�
12
A1 N2
(ii) There are 3 ways such that X � 10 (A1) for correct value
P( X � 10)
3
�
36
1
�
12
A1 N2
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